What are the main differences between an RRSP and a 401k retirement account?

The main differences between an RRSP and a 401k retirement account are that RRSPs are used in Canada while 401ks are used in the United States. RRSP contributions are tax-deductible, while 401k contributions are made with pre-tax dollars. Additionally, RRSPs have more flexible withdrawal rules compared to 401ks.